The present invention relates to the identification of a gene which controls fruit size and/or cell division in plants, the proteins encoded by that gene, and uses thereof.
In natural populations, most phenotypic variation is continuous and effected by alleles at multiple loci. Although this quantitative variation fuels evolutionary change and has been exploited in the domestication and genetic improvement of plants and animals, the identification and isolation of the genes underlying this variation has been difficult.
The most conspicuous and, perhaps, most important quantitative traits in plant agriculture are those associated with domestication (Doebley et al., xe2x80x9cGenetic and Morphological Analysis of a Maize-Teosinte F2 Population: Implications for the Origin of Maize,xe2x80x9d PNAS 87: 9888-9892 (1990)). Key adaptations to survival in the wild were dramatically modified by early humans; fruit-bearing crop plants are a prime example. Dramatic and relatively rapid changes in fruit size have accompanied the domestication of virtually all fruit-bearing crop species, including tomato, watermelon, apple, banana, grape, berries and a vast assortment of other tropical, subtropical, and temperate species (J. Smartt et al., Evolution of Crop Plants (Longman Group, United Kingdom, (1995)). These changes have benefited mankind but have often been at the expense of the plant""s seed production, dispersal, and survival under natural conditions. The progenitor of domesticated tomato (Lycopersicon esculentum Mill.) most likely had fruit less than 1 cm in diameter and only a few grams in weight (Rick, C. M., xe2x80x9cTomato,xe2x80x9d Scientific American 239:76 (1978)). Such fruit were large enough to contain hundreds of seeds and yet small enough to be dispersed by small rodents or birds. In contrast, modern tomatoes can weigh as much as 1,000 grams and can exceed 150 cm in diameter. While it is known that the transition from small to large fruit occurred numerous times during the domestication of crop plants (J. Smartt, et al. Evolution of Crop Plants (Longman Group, United Kingdom, (1995)) and that it is quantitatively controlled (Paterson et al., xe2x80x9cMendelian Factors Underlying Quantitative Traits in Tomato: Comparison Across Species, Generations, and Environments,xe2x80x9d Genetics 127(1):181-97 (1991)), the molecular basis of this transition has thus far been unknown.
Using the approach of quantitative trait locus (QTL) mapping (Lander et al., xe2x80x9cMapping Mendelian Factors Underlying Quantitative Traits Using RFLP Linkage Maps,xe2x80x9d Genetics 121(1):185-99 (1989) published erratum appears in Genetics 136 (2):705 (1994)); Tanksley S. D., xe2x80x9cMapping Polygenes,xe2x80x9d Annu Rev Genet 27:205-33 (1993)), most of the loci involved in the evolution and domestication of tomato from small berries to large fruit have been genetically mapped (Grandillo et al., xe2x80x9cIdentifying the Loci Responsible for Natural Variation in Fruit Size and Shape in Tomato,xe2x80x9d Theor. Appl. Gen. 99:978 (1999)). One of these QTLs, fw2.2, appears to have been responsible for a key transition during domestication: all wild Lycopersicon species examined thus far contain small fruit alleles at this locus whereas modern cultivars have large fruit alleles (Alpert et al., xe2x80x9cFW-2.2xe2x80x94A Major QTL Controlling Fruit Weight Is Common to Both Red-Fruited and Green-Fruited Tomato Species,xe2x80x9d Theor. Appl. Gen. 91: 994 (1995)). What is needed to further the current understanding of the genetic regulation of fruit size in plants is the identification of the nucleic acid sequence of the fw2.2 gene and of the protein product encoded by the cDNA of that gene.
The present invention is directed to achieving these objectives.
The present invention relates to an isolated nucleic acid molecule encoding a protein which regulates fruit size and/or cell division in plants.
The present invention also relates to an isolated protein which regulate fruit size and/or cell division in plants.
The present invention also relates to a method of regulating fruit size in plants by transforming a plant with a nucleic acid molecule of the present invention under conditions effective to regulate fruit size in the plant.
The present invention also relates to a method of regulating cell division in plants by transforming a plant with a nucleic acid molecule of the present invention under conditions effective to regulate cell division in the plant.
The present invention provides an important advance in the study of morphogenesis in plants, and provides new opportunities for understanding and utilizing natural variation. In particular, a greater understanding of the genetic regulation of fruit size and/or cell division in plants provides a means for the generation of agronomically superior crops through genetic manipulation.